Large Sitemap Issue

Hi all so i created a wordpress site with near 900K pages and finally got it running. Now i need a sitemap and although the site is running on a pretty powerful dedicated server none of the wordpress plugins can generate the sitemap (i have tried them all). Some cant even generate the sitemap others partially generate sitemap with correct URL structures and others can generate the 900K sitemap but with partially incorrect URLs. The Better WordPress Google XML Sitemaps plugin got the closest and can generate a list easily but the URLs are partially incorrect (im using custom posts). I have a list in csv of every single URL for my wordpress site but im wondering 1) if anyone know of an easy way to convert this to a split sitemap that is google friendly or 2) any kind of solution for creating a large wordpress sitemap.

Thanks